1. Field of the Invention
The present invention relates to a golf club shaft.
2. Description of the Related Art
A so-called carbon shaft has been widely used. In the carbon shaft, CFRP (carbon fiber reinforced plastic) is normally used. The fiber reinforced resin has an excellent specific strength and specific rigidity. The carbon shaft can contribute to the weight saving of a club. The weight saving of the club can contribute to the increase of a flight distance.
A bias layer is normally provided in the carbon shaft. The bias layer can enhance torsional rigidity. The directional stability of a hit ball can be improved by the improvement of the torsional rigidity.
Japanese Patent Application Laid-Open No. 2011-147543 (FIGS. 5, 6 and 8 or the like) discloses a shaft having a first bias layer, a second bias layer, and a third bias layer. Japanese Patent Application Laid-Open No. 2010-63778 (FIGS. 5 and 6 or the like) discloses a shaft having a first bias layer, a second bias layer, and a third bias layer. Japanese Patent Application Laid-Open No. 2009-60983 discloses a shaft having at least two bias set layers. Japanese Patent Application Laid-Open No. 2007-185253 (FIG. 2 or the like) discloses a shaft having a first full length layer II, a second full length layer III, and a third full length layer IV. Japanese Patent Application Laid-Open No. 2004-57642 (Claim 1, FIG. 2 or the like) discloses a shaft having a reinforced prepreg sheet as an outermost layer located on a shaft small diameter side.